Apparatus and method for printing solder paste

ABSTRACT

A filling squeegee and a scraping squeegee are provided. The filling squeegee is moved in a state without contact with a surface of a mask thereby to fill a solder paste in openings of the mask, then the unnecessary solder paste on the surface of the mask is scraped by the scraping squeegee. The solder paste is prevented from being filled in the openings improperly or scraped improperly even if a speed of the squeegee is increased, so that the solder paste is printed stably on circuit boards.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an apparatus and a method forprinting, applying solder paste onto surfaces of circuit boards to beprinted.

[0002] In the prior art of manufacturing electronic circuit boards,solder paste has been primarily used to solder electronic componentssuch as chips or the like onto printed boards. A solder paste printingapparatus has been employed to print, apply the solder paste in arequired pattern.

[0003] A squeegee head loaded to a conventional solder paste printingapparatus 100 is constituted, for instance, as shown in FIG. 20.Generally, a squeegee head 102 moves from left to right and from rightto left in FIG. 20 alternately for every printed board 5 to print thesolder paste. A right squeegee 101 a is used for printing in the rightdirection, namely, from left to right in FIG. 20, and a left squeegee101 b is for printing in the opposite left direction.

[0004] An operation for printing the solder paste to the printed board 5by the conventional solder paste printing apparatus 100 will bedescribed with reference to FIGS. 20-22. In FIGS. 20-22, referencesrespectively indicate: 3 a mask having openings 4 formed in a requiredpattern; 5 a printed board; 6 a land to which a solder paste 7 isprinted; and 8 a solder resist. The above-mentioned required pattern ofthe mask 3 is a pattern in which openings 4 are formed corresponding tolands 6 on the printed board 5.

[0005] Firstly, in printing in the right direction, the printed board 5is positioned and overlapped with the mask 3 so that the openings 4agree with the lands 6. Thereafter, while the left squeegee 101 b iskept raised, the right squeegee 101 a is lowered to bring a squeegeefront end part 103 in touch with a surface 3 a of the mask 3 with asuitable printing pressure. In this state, the right squeegee 111 a islinearly moved in the right direction, thereby to fill the solder paste7 provided at the surface 3 a of the mask 3 into the openings 4 of themask 3. The printed board 5 is separated from the mask 3 after the rightsqueegee 101 a is moved to the right end of the mask 3, when theprinting is finished. Meanwhile, in the case of printing in the leftdirection, the printed board 5 is positioned and overlapped with themask 3, similar to the above printing in the right direction. Then, theleft squeegee 101 b is descended while the right squeegee 101 a is heldup, to bring the squeegee front end part 103 in touch with the mask 3.The operation afterwards is the same as in the case of printing in theright direction. By repeating the operations in the right direction andleft direction alternately for every printed board 5, the solder paste 7is continuously printed, applied onto the lands 6 of each printed board5 via the mask 3.

[0006] In the conventional solder paste printing apparatus 100, thesqueegee 101 a or 101 b is moved while the front end part 103 of thesqueegee is kept in touch with the surface 3 a of the mask 3 with asuitable printing pressure. As is made clear from this fact, each of theconventional squeegees 101 a, 101 b executes two kinds of operations,i.e., a scraping operation of scraping the solder paste 7 at the surface3 a of the mask 3 and a filling operation of filling the solder paste 7to openings 4 of the mask 3, which will be described with reference toFIGS. 21 and 22.

[0007]FIGS. 21 and 22 are enlarged views of the printing squeegee 101 a,etc. when the printing is carried out in the right direction. As shownin FIG. 21, when the right squeegee 101 a is descended to bring thefront end part 103 in touch with the surface 3 a of the mask 3 and movedlinearly in the right direction, the right squeegee 101 a reaching thesolder paste 7 fed to the surface 3 a of the mask 3 moves while scrapingthe solder paste. The scraped solder paste 7 flows accompanying a rotarymovement called rolling as indicated by an arrow I in FIG. 22. At thistime, a fluid pressure is generated inside the solder paste 7. When theright squeegee 101 a moves further right to reach the opening 4 of themask 3 in the above condition, the solder paste 7 is pressed into theopenings 4 because of the above-described fluid pressure, in otherwords, the solder paste 7 is filled in the openings 4. A pressure withwhich the solder paste 7 is pressed into the openings 4 will be denotedas a “filling pressure” hereinbelow.

[0008] Supposing a coordinate system as shown in FIG. 23 to the printingsqueegee 101 a, when a viscosity of the solder paste 7 is η, an angle ofthe surface 3 a of the mask 3 to a face 104 of the printing squeegee 111a facing the surface 3 a (referred to as a “squeegee angle” hereinafter)is α, a speed of the moving squeegee 101 a (referred to as a “squeegeespeed”) is v, it is known that a fluid pressure p produced inside thesolder paste 7 is expressed by an equation below.

p=(2ηv/r)*(A sin θ+B cos θ)  (1

[0009] wherein r is an optional position in the polar coordinate systemof FIG. 23, θ is an angle of the surface 3 a of the mask 3 to the abover, A=sin² α/(α²−sin² α) and B=(α−sin α*cos α)/(α²−sin² α).

[0010] From the above expression (1), a fluid pressure distribution inthe solder paste 7 and a pressure distribution at the face 104 of theprinting squeegee 101 a are as indicated in FIG. 24. Specifically, ashaded part 105 in FIG. 24 is where the fluid pressure p, namely,filling pressure is generated.

[0011] In the meantime, a print time for printing the solder paste isrequired to be reduced in the printing process from the viewpoint ofimproving productivity. However, if the squeegee speed v is made fasterin order to shorten the print time in the conventional solder pasteprinting apparatus 100, the amount of the solder paste 7 filled in theopenings 4 of the mask 3 becomes scarce as indicated in FIG. 25,resulting in printing failures with non-filled parts 9 and hinderingstable printing. The non-filled part 9 is not generally brought about,for example, if ink is printed in a method of screen printing, but isgiven rise to when a paste-like substance of a mixture of a highviscosity flux with powder solder, e.g., the solder paste 7 or the likeis used. That is, the non-filled part 9 is caused by the powder solder.In other words, there is an issue that it is impossible to realize areduction of the print time through an increase of the squeegee speed vin the conventional solder paste printing apparatus 100.

[0012] The non-filled part 9 resulting from an increase of the squeegeespeed v is a phenomenon as follows. When the squeegee speed v isincreased more than in the prior art, a time for the front end part 103of the printing squeegee 101 a to pass over the opening 4 is reduced. Inconsequence, a time for the solder paste 7 to be filled in the opening 4(referred to as a “fill time”) is naturally shortened. The fillingpressure becomes maximum when r=0, i.e., at a contact point of the frontend part 103 of the printing squeegee 101 a and the surface 3 a of themask 3, as is understood from the expression (1) and FIGS. 23 and 24.Although P_(r)=P₇₄=∞ is theoretically held when r=0, the contact pointis practically a stagnation point and accordingly shows a maximum value.

[0013] While the filling pressure itself is raised when the squeegeespeed v is increased, a high pressure range is narrow as is seen fromthe pressure distribution of the shaded part of FIG. 24. In addition,since the front end part 103 passes over the opening 4 instantaneously,the fill time cannot be secured enough. As a result of this, thenon-filled part 9 is formed.

[0014] In order to prevent an occurrence of the non-filled parts 9, fromthe expression (1), it can be considered that the squeegee angle αshould be reduced and at the same time, the filling pressure should beincreased, whereby the filling is completed even in a short fill time.However, since the conventional printing squeegee 101 a performs twooperations, namely, the filling operation to the solder paste 7 and thescraping operation from the surface 3 a of the mask 3 as describedabove, the front end part 103 is deformed large if the filling pressureis increased, making it impossible to scrape the solder paste 7 from thesurface 3 a of the mask 3. The solder paste 7 is left at the surface 3 aof the mask 3, as shown in FIG. 26. In the event that the front end part103 of the squeegee 101 a is further tightly pressed in touch with thesurface 3 a of the mask 3 so as to prevent the solder paste 7 fromremaining at the surface 3 a of the mask 3, as shown in FIG. 27, thesolder paste 7 is actually scraped, whereas the amount of thedeformation of the front end part 103 of the squeegee is increased dueto the larger contact pressure. Therefore, when the front end part 103reaches the opening 4, a part of the front end part 103 enters theopening 4 subsequent to the restoration of the front end part 103,undesirably scraping the solder paste 7 already filled in the opening 4.Moreover, the powder solder included in the solder paste 7 facilitatesthe scraping. The amount of the solder paste 7 filled in the opening 4is hence decreased, obstructing stable printing.

[0015] Under the circumstances, when a printing is performed,conventionally, a worker sets, adjusts and changes printing conditionsbased on experiments in order to fully achieve both the scrapingoperation and the filling operation and print the solder paste stably.In other words, the printing conditions are set, adjusted and changedwith a great personal difference and to maintain stable printing is ahard task as an issue.

SUMMARY OF THE INVENTION

[0016] The present invention is devised to solve the above-describedinconveniences, and has for its object to provide a solder pasteprinting apparatus and a solder paste printing method whereby a solderpaste can be printed stably even when a print time is increased ascompared with the prior art.

[0017] In accomplishing these and other aspects, according to a firstaspect of the present invention, there is provided a solder pasteprinting apparatus wherein a squeegee device moves in a printingdirection to a surface of a mask having openings formed therein, therebyto print and apply solder paste on the surface via the openings to aface of a circuit board positioned at a rear face of the mask, saidsqueegee device comprising: a filling squeegee having a front end keptin a noncontact state via a gap to the surface at the time of printing,and filling the solder paste into the openings while moving in theprinting direction; and a scraping squeegee arranged behind the fillingsqueegee in the printing direction, moving in the same direction as thefilling squeegee while keeping touch with the surface at the time ofprinting thereby to remove unnecessary solder paste on the surface.

[0018] According to a second aspect of the present invention, there isprovided a solder paste printing apparatus according to the firstaspect, wherein the scraping squeegee is provided for each directionbehind the filling squeegee with respect to the printing direction in acase where the squeegee reciprocates to the surface of the mask.

[0019] According to a third aspect of the present invention, there isprovided a solder paste printing apparatus according to the secondaspect, wherein the filling squeegee is divided to two in the printingdirection.

[0020] According to a fourth aspect of the present invention, there isprovided a solder paste printing apparatus according to any one of thefirst to third aspects, further comprising an angle setting device forsetting the scraping squeegee so that an angle of the scraping squeegeein an axial direction thereof to the surface of the mask is an optionalacute or obtuse angle.

[0021] According to a fifth aspect of the present invention, there isprovided a solder paste printing apparatus according to the fourthaspect, wherein the scraping squeegee is inclined with the obtuse angleby the angle setting device.

[0022] According to a sixth aspect of the present invention, there isprovided a solder paste printing apparatus according to the fourthaspect, wherein the scraping squeegee is inclined with the acute angleby the angle setting device thereby to fill the solder paste into theopenings as well as remove the unnecessary solder paste.

[0023] According to a seventh aspect of the present invention, there isprovided a solder paste printing apparatus according to any one of thefirst to sixth aspects, wherein the scraping squeegee is disposed sothat an extending direction of a line of contact between the scrapingsqueegee and the surface of the mask intersects with an extendingdirection of a side edge part defining one of the openings.

[0024] According to an eighth aspect of the present invention, there isprovided a solder paste printing apparatus according to any one of thefirst to seventh aspects, wherein a face of the filling squeegeeopposite to the surface of the mask forms a filling pressuring facewhich is inclined upward from the front end in the printing direction soas to press the solder paste to the surface and fill the solder paste tothe openings.

[0025] According to a ninth aspect of the present invention, there isprovided a solder paste printing apparatus according to the eighthaspect, further comprising a filling adjustment device for adjustingfilling of the solder paste to the openings by varying at least one of asize of the gap and an intersection angle of the filling pressuring faceand the surface.

[0026] According to a tenth aspect of the present invention, there isprovided a solder paste printing apparatus according to the ninthaspect, further comprising a filling pressure detector for detecting achange of a filling pressure of the solder paste filled into theopenings at the time of printing, and a control device for controllingthe filling adjustment device based on the filling pressure detected bythe filling pressure detector.

[0027] According to an eleventh aspect of the present invention, thereis provided a solder paste printing apparatus according to the tenthaspect, wherein the filling pressure detector is a reaction forcedetector for detecting a reaction force which is a sum of the fillingpressures of the solder paste acting to the whole filling pressuringface at the time of printing.

[0028] According to a twelfth aspect of the present invention, there isprovided a solder paste printing apparatus according to the tenthaspect, wherein the filling pressure detector is a pressure detector setat the filling pressuring face for detecting the filling pressure of thesolder paste directly.

[0029] According to a thirteenth aspect of the present invention, thereis provided a solder paste printing method comprising: moving a fillingsqueegee in a printing direction at time of printing while keeping afront end of the filling squeegee in a noncontact state via a gap to asurface of a mask having openings formed therein, thereby filling asolder paste on the surface to the openings; and removing unnecessarysolder paste on the surface by a scraping squeegee moving in touch withthe surface in the printing direction.

[0030] According to a fourteenth aspect of the present invention, thereis provided a solder paste printing method according to the thirteenthaspect, wherein the scraping squeegee is set so that an angle of thescraping squeegee in an axial direction thereof to the surface of themask is an optional acute or obtuse angle.

[0031] According to a fifteenth aspect of the present invention, thereis provided a solder paste printing method according to the fourteenthaspect, wherein, when the scraping squeegee is set with the obtuseangle, the scraping squeegee removes the unnecessary solder pastewithout adversely influencing the solder paste filled in the openings.

[0032] According to a sixteenth aspect of the present invention, thereis provided a solder paste printing method according to the fourteenthaspect, wherein, when the scraping squeegee is set with the acute angle,the scraping squeegee fills the solder paste to the openings as well asremoves the unnecessary solder paste.

[0033] According to a seventeenth aspect of the present invention, thereis provided a solder paste printing method according to any one of thethirteenth to sixteenth aspects, wherein the scraping squeegee is set sothat an extending direction of a line of contact between the scrapingsqueegee and the surface of the mask intersects with an extendingdirection of a side edge part defining one of the openings.

[0034] According to an eighteenth aspect of the present invention, thereis provided a solder paste printing method according to any one of thethirteenth to seventeenth aspects, wherein a face of the fillingsqueegee opposite to the surface of the mask forms a filling pressuringface which is inclined upward from the front end in the printingdirection so as to press the solder paste to the surface and fill thesolder paste to the openings.

[0035] According to a nineteenth aspect of the present invention, thereis provided a solder paste printing method according to the tenthaspect, wherein a change of a filling pressure of the solder paste whenthe solder paste is filled by the filling squeegee to the openings atthe time of printing is detected by a filling pressure detector, and atleast one of an intersection angle of the filling pressuring face andthe surface and a size of the gap is adjusted based on the detectedfilling pressure, thereby to change printing condition.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] These and other aspects and features of the present inventionwill become clear from the following description taken in conjunctionwith the preferred embodiments thereof with reference to theaccompanying drawings, in which:

[0037]FIG. 1 is a diagram showing the schematic structure of a solderpaste printing apparatus according to one embodiment of the presentinvention;

[0038]FIG. 2 is a diagram of a front end part of a filling member of afilling squeegee of FIG. 1;

[0039]FIG. 3 is a diagram of a model for obtaining a filling pressure ofsolder paste by the filling member of the filling squeegee of FIG. 1;

[0040]FIG. 4 is a diagram of a pressure distribution obtained from themodel of FIG. 3;

[0041]FIG. 5 is a diagram of the filling member of the filling squeegeeof FIG. 1 in a different embodiment;

[0042]FIG. 6 is a diagram of the filling squeegee of FIG. 1 in adifferent embodiment;

[0043]FIG. 7 is a diagram of the filling member of the filling squeegeeof FIG. 1 in a yet different embodiment;

[0044]FIG. 8 is a flow chart of the operation of the solder pasteprinting apparatus of FIG. 1;

[0045]FIG. 9 is a diagram of a modified example of the solder pasteprinting apparatus in FIG. 1;

[0046]FIG. 10 is a diagram of an arrangement relation between a line ofcontact of the scraping squeegee and mask, and the opening in the solderpaste printing apparatus of FIG. 9;

[0047]FIG. 11 is a diagram of a state when the solder paste is scrapedwhile a side face of the scraping squeegee is set at an obtuse angle toa surface of the mask in the solder paste printing apparatus of FIG. 9;

[0048]FIG. 12 is a diagram of a model explanatory of why the solderpaste is scraped by the scraping squeegee of FIG. 11;

[0049]FIG. 13 is a diagram of a state when the solder paste is filled inthe openings while the side face of the scraping squeegee is set at anacute angle to the surface of the mask in the solder paste printingapparatus of FIG. 9;

[0050]FIG. 14 is a diagram when the angle of the side face of thescraping squeegee to the surface of the mask is changed variously in thesolder paste printing apparatus of FIG. 9;

[0051]FIG. 15 is a diagram when the angle of the side face of thescraping squeegee to the surface of the mask is changed variously in thesolder paste printing apparatus of FIG. 9;

[0052]FIG. 16 is a diagram when the angle of the side face of thescraping squeegee to the surface of the mask is changed variously in thesolder paste printing apparatus of FIG. 9;

[0053]FIG. 17 is a diagram of a further modification of the solder pasteprinting apparatus of FIG. 1;

[0054]FIG. 18 is a perspective view of a filling member of a fillingsqueegee in the solder paste printing apparatus of FIG. 17;

[0055]FIG. 19 is a sectional view of the filling member of FIG. 18;

[0056]FIG. 20 is a diagram showing the schematic structure of aconventional solder paste printing apparatus;

[0057]FIG. 21 is a diagram showing a state when printing is conductedwith the use of a squeegee of FIG. 20;

[0058]FIG. 22 is a diagram of a state when the solder paste is filled inthe openings by the squeegee of FIG. 20;

[0059]FIG. 23 is a diagram of a model for obtaining a filling pressureproduced to the solder paste by the squeegee of FIG. 20;

[0060]FIG. 24 is a diagram of a distribution of a filling pressuregenerated in the solder paste by the squeegee of FIG. 20;

[0061]FIG. 25 is a diagram of a state when non-filled parts are broughtabout in the openings of the mask;

[0062]FIG. 26 is a diagram of a state where the solder paste is left onthe surface of the mask when a front end part of the squeegee of FIG. 20is deformed large;

[0063]FIG. 27 is a diagram of a state where the solder paste filled inthe openings is scraped when the front end part of the squeegee of FIG.20 is deformed large;

[0064]FIG. 28 is a diagram of a state when a reaction force detector isset to the printing squeegee in the conventional solder paste printingapparatus of FIG. 20; and

[0065]FIG. 29 is a diagram explanatory of how the reaction forcedetector of FIG. 28 cannot detect a reaction force of the solder paste.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0066] Before the description of the present invention proceeds, it isto be noted that like parts are designated by like reference numeralsthroughout the accompanying drawings.

[0067] An apparatus and a method for printing a solder paste accordingto one embodiment of the present invention will be described withreference to the drawings. The printing method is carried out by theprinting apparatus. Parts functioning the same or similarly aredesignated by the same reference numerals throughout the drawings, thedescription of which will be omitted here. In the specification, asolder paste is a paste-like solder obtained by mixing powder solderwith a high viscosity flux. An up-down driving device 11 and an anglevariable device 12 for a filling squeegee 10 which will be describedlater correspond to an embodiment fulfilling the function of the fillingadjustment device. A reaction force detector 13 and pressure detectors532 a, 532 b to be described later correspond to an embodiment achievingthe function of the filling pressure detector.

[0068]FIG. 1 is a schematic diagram in the neighborhood of a squeegee ina solder paste printing apparatus 51 of the embodiment. The squeegeemoves both in the right and in the left directions in the solder pasteprinting apparatus 51.

[0069] In addition to a scraping squeegee 14 a for use in printing inthe right direction and a scraping squeegee 14 b for use in printing inthe left direction, the solder paste printing apparatus 51 has a fillingsqueegee 10 arranged at a position between the squeegees 14 a and 14 bin a printing direction for filling a solder paste 7 to openings 4 of amask 3.

[0070] Each of the scraping squeegees 14 a, 14 b scraping unnecessarysolder paste 7 on the mask 3 at the time of printing is moved up anddown between a standby position 18 and a scrape position 19 by anup-down driving device 15, 16 mounted to a bed plate 17 of a squeegeehead constituting the printing apparatus 51. The bed plate 17 is movedin the left, right printing direction by a driving device 49 controlledby a control device 48. In FIG. 1 showing a state when the printing isconducted in the right direction, the scraping squeegee 14 a is loweredto the scrape position 19, while the scraping squeegee 14 b is raised atthe standby position 18. When the scraping squeegee 14 a, 14 b is at thescrape position 19, a front end part 20 of each squeegee comes in touchwith a surface 3 a of the mask 3 so that a suitable pressure isimpressed to the surface 3 a. Although a side face 21 of the front endpart 20 of each of the scrape squeegees 14 a, 14 b is indicated toextend orthogonally to the surface 3 a in FIG. 1, the side face 21 ofeach of the squeegees 14 a, 14 b is inclined at the actual time ofprinting with an optional acute or obtuse angle to the surface 3 a ofthe mask 3, for example, as shown in FIGS. 11, 13, thereby scrapingunnecessary solder paste 7 on the surface 3 a. The unnecessary solderpaste 7 on the surface 3 a is a solder paste present swelling over thesurface 3 a and openings 4 at the surface 3 a and openings 4 of the mask3.

[0071] The driving device 49 and up-down driving devices 15, 16 arerespectively connected to the control device 48 controlling operationsof the solder paste printing apparatus 51.

[0072] The filling squeegee 10 schematically has a filling member 22 anda holding member 23 holding the filling member 22 and is coupled via thereaction force detector 13 to a driving shaft 11 a of an up-down drivingdevice 11 therefor mounted to the bed plate 17. The up-down drivingdevice 11 is connected to the control device 48 and driven via thecontrol device 48 based on output information from the reaction forcedetector 13 thereby to move the driving shaft 11 a up and down as willbe described in detail later.

[0073] In the embodiment, one filling squeegee 10 is provided for both,right and left printing directions. The filling member 22 is formedschematically in the shape of the bottom of a ship as shown in thefigure. A face at a front end part of the filling member 22 opposing thesurface 3 a constitutes, as is illustrated in a detailed manner in FIG.2, a filling pressuring face 25 inclined upward from a front end 24 ofthe filling member 22 to each printing direction. The filling member 22can be formed of rubber, metal or the like material used in theconventional squeegees. On the occasion of printing, the fillingsqueegee 10 is arranged so that the front end 24 has a gap H2 of a sizeh2 to the surface 3 a, and moreover, an intersecting part 26 between aside face 22 a at the side of the printing direction of the fillingmember 22 and the filling pressuring face 25 assumes a gap H1 of a sizeh1 to the surface 3 a.

[0074] Owing to the filling squeegee 10 with the above-described fillingmember 22 and the scraping squeegees 14 a, 14 b provided in theapparatus, a part 9 is never left without being filled with the solderpaste 7 in the openings 4 of the mask 3 unlike the conventionalapparatus even when a squeegee speed of the filling squeegee 10 isincreased, and stable printing is achieved. The reason for this will bedescribed below.

[0075] The filling pressure generated when the solder paste 7 is filledin the openings 4 by the filling squeegee 10 will be depicted withreference to FIG. 2. In the state shown in FIG. 2, when the fillingsqueegee 10 is moved right as indicated by an arrow, the solder paste 7enters from the side of the gap H1 to the filling pressuring face 25 ofthe filling member 22 and flows out of the gap H2. This phenomenon canbe explained by an example of a flow of a substance entering a narrowwedge-like gap, and concretely, a model shown in FIG. 3 is used here todepict the phenomenon. The model is a generally known one used in thedescription of fluid lubrication at a bearing or the like and isapproximate to the filling member 22 of the right half from the gap H2to the gap H1. In FIG. 3, supposing that a size of a gap at the entranceside of a fluid between a wall body 301 and a reference face. 302 is h₁,a size of the gap at the exit side is h₂, a distance between theentrance and exit gaps is L, a size of a gap between the wall body 301and reference face 302 at a distance x from the entrance gap is h, aspeed of the moving wall body 301 is v, and a viscosity of the fluid isη, a pressure p′ generated because of a flow of the fluid at thedistance x is expressed by the following equation. A distribution of thepressure p′ is as shown in FIG. 4, as is well known.

p′=(6ηvL/(h ₁ ² −h ₂ ²))*((h ₁ −h)(h−h ₂)/h ²)  (2)

[0076] The filling pressure and a pressure distribution generated to thesolder paste 7 by the filling member 22 of the filling squeegee 10 canbe considered in the same way. In comparing a shaded part 303 in FIG. 4with the shaded part 105 in FIG. 24, it is clear that the fillingpressure is generated high in a wide range with the employment of thefilling squeegee 10. Accordingly, the solder paste is perfectly filledinto the openings 4 even if the fill time is short. A filling defect orfailure such as the non-filled part, etc. is never brought about even atan increased squeegee speed, thus accomplishing stable printing.

[0077] The above-described filling member 22 is held by the holdingmember 23 in a manner to be able to swing both in the right and in theleft printing directions at a pin 27 coaxial with the driving shaft 11a. As will be described later, the holding member 23 is provided withthe angle variable device 12 such as a motor or a cylinder so as to makevariable an intersection angle of the filling pressuring face 25 of thefilling member 22 and the surface 3 a of the mask 3 and maintain thefilling member 22 which can swing centering the pin 27, properly at theintersection angle. One end of a main body of the angle variable device12 is supported rotatably by the holding member 23 and a front end partof a driving shaft 12 a which can move forward and backward to the mainbody is rotatably coupled to a shoulder part 22 a of the filling member22. Therefore, the filling member 22 swings at a fulcrum of the pin 27when the driving shaft 12 a is moved forward and backward. The anglevariable device 12 is also connected to the control device 48, changingthe intersection angle by advancing or retreating the driving shaft 12 aunder the control of the control device 48.

[0078] According to the present embodiment, the holding member 23 isconnected to the driving shaft 11 a of the up-down driving device 11 viathe reaction force detector 13 such as a load cell so as to detect areaction force acting to the filling pressuring face 25 of the fillingmember 22 via the solder paste 7 at the time of printing. The reactionforce cannot be detected simply by providing the conventional solderpaste printing apparatus with the reaction force detector 13. The reasonwill be discussed with reference to FIG. 28. The front end part of theconventional printing squeegee 101 a moves while keeping touch with thesurface 3 a of the mask 3, and consequently is deformed large due to afriction, as shown in FIG. 29. What's worse, a contact point between thefront end part of the squeegee 101 a and the surface 3 a of the mask 3is not present on a vertical direction of the reaction force detector.When the contact point of the squeegee 101 a is pressed up by thereaction force of the solder paste 7, an end part of the squeegee 101 aat the side opposite to the contact point is pulled towards the mask 3.The reaction force detector virtually detects this tensile force to themask 3 in spite of the reaction force by the solder paste 7 acting tothe squeegee 101 a. The reaction force detector hence cannot detect thereaction force of the solder paste 7. In contrast, the filling squeegee10 of the printing apparatus 51 of the embodiment moves without touchwith the surface 3 a of the mask 3, whereby the reaction force of thesolder paste 7 can be detected.

[0079] As is clear from FIG. 3 and expression (2), the reaction forceacting to the filling pressuring face 25 can be obtained by integratingthe pressure p′ in a range of x=0−L. A state of the filling pressure canbe known from the reaction force of the solder paste 7 detected by thereaction force detector 13. Moreover, the pressure p′ can be changed byadjusting the sizes h1 and h2 of the gaps H1 and H2, as is understoodfrom the expression (2), and the sizes h1 and h2 can be adjusted bydriving at least either of the up-down driving device 11 and anglevariable device 12 of the squeegee 10.

[0080] For the above purpose, the reaction force detector 13 isconnected to the control device 48. The control device 48 controls thedrive of the up-down driving device 11 based on information of thereaction force detected by the reaction force detector 13 thereby tomove the filling member 22 up/down via the driving shaft 11 a so as toadjust the size h2 of the gap H2 or the size h1 of the gap H1 to preventthe non-filled part 9 from being formed in the openings 4 of the mask 3,or the drive of the angle variable device 12 to adjust the intersectionangle. For example, even if physical properties of the solder paste 7,particularly the viscosity η is changed due to an environmental changeor the like influence and the filling pressure is changed or, the kindof the solder paste 7 is changed when the type of products is to beswitched, etc., the control device 48 operates at least one of theup-down driving device 11 and angle variable device 12 so that theinformation of the reaction force of the solder paste 7 detected by thedetector 13 is approximated to a preset reaction force value or areaction force value before the type is switched. In this manner, atleast one of a height of the filling squeegee 10 and the intersectionangle is changed and the sizes h1 and h2 are adjusted, in other words,printing conditions are automatically adjusted and changed, achievingstable printing. The controlling to the up-down driving device 11 andangle variable device 12 by the control device 48 may be carried out inreal time along with the movement of the filling squeegee 10 or forevery circuit board or at every time of printing.

[0081] The printing conditions are thus automatically adjusted andchanged, maintaining stable printing and shortening a work time.

[0082] Although the filling pressuring face 25 of the filling member 22of the filling squeegee 10 is flat in the embodiment, the face 25 is notlimited to this, but may be a curved face projecting to the surface 3 aas exemplified in FIG. 5. In other words, a shape of the fillingpressuring face 25 is not specified so long as the size h1 of the gapbetween the filling pressuring face 25 and the surface 3 a of the mask 3is larger than the size h2 with respect to the printing direction, i.e.,h1>h2 is satisfied. At the same time, the front end 24 of the fillingmember 22 may be sharp as in FIG. 2 or flat parallel to the surface 3 aover a suitable length in the printing direction as shown in FIG. 7.

[0083] The reaction force detector 13 and angle variable device 12 canbe set at any positions so long as respective functions are fulfilled,not restricted to the above-described positions.

[0084] Since the printing apparatus 51 is a type moving both in theright and left directions, the printing apparatus is equipped with twoscraping squeegees 14 a, 14 b. The printing apparatus may be a typemoving in either direction only, and in that case, the scraping squeegee14 a or 14 b corresponding to the moving direction is provided.

[0085] In the present printing apparatus 51, the filling member 22 ofthe filling squeegee 10 is formed to be symmetric right and left and thesame filling squeegee 10 is used for both printing directions. However,as shown in FIG. 6, the filling squeegee may be divided to a rightfilling squeegee 305 a and a left filling squeegee 305 b to operate andprint individually. To install two filling squeegees 305 a, 305 b hasthe following merit. In the case of the single filling squeegee 10, whenthe height or the intersection angle of the squeegee 10 is notcontrolled in real time, but is set before the printing is started, andif the height or intersection angle of the squeegee 10 is changed duringprinting in the right direction, the up-down driving device 11 or anglevariable device 12 should be operated before the start of the leftprinting in order to obtain the same printing conditions in the leftprinting as well. To contrary, when two filling squeegees 305 a, 305 bare provided, the up-down driving devices 11 and angle variable devices12 can be driven separately beforehand in accordance with the printingdirections.

[0086] The operation when the solder paste is printed with the use ofthe above-constituted printing apparatus 51 will be described withreference to FIG. 8. The up-down driving device(s) 11 and angle variabledevice(s) 12 are controlled in real time in the description hereinbelow.

[0087] The following operations are carried out in step 1 (indicated by“S1” in FIG. 8). A predetermined amount of the solder paste 7 issupplied to the surface 3 a of the mask 3. When the printing isperformed in the right direction, the printed board 5 is positioned andoverlapped with the mask 3 and the filling squeegee 10 and rightscraping squeegee 14 a are descended respectively by the up-down drivingdevices 11 and 15. At this time, the front end part 20 of the scrapingsqueegee 14 a is brought in touch with the surface 3 a of the mask 3with a suitable pressing force. The filling squeegee 10 is, as shown inFIG. 2, not in touch with the surface 3 a of the mask 3, securing thegap H2 of the predetermined size h2. The squeegee 10 is moved down sothat the gap H2 is located behind the supplied solder paste 7 in theprinting direction.

[0088] In step 2, while the state is maintained, the bed plate 17 ismoved right by the driving device 49 and the filling squeegee 10 andscraping squeegee 14 a are moved linearly in the right printingdirection. The filling of the solder paste 7 to the openings 4 of themask 3 by the filling squeegee 10 is thus started.

[0089] The reaction force acting to the filling squeegee 10 is detectedby the reaction force detector 13 in step 3. Whether or not the detectedreaction force is, for example, within the preset reaction force valueas described before is judged in step 4. When the detected reactionforce is outside a proper range, the control device 48 drives at leastone of the up-down driving device 11 and angle variable device 12 tobring the detected reaction force within the proper range in step 5. Atleast one of the height and the intersection angle of the fillingsqueegee 10 is changed accordingly.

[0090] In step 6, a layer of the solder paste 7 formed on the surface 3a of the mask 3 because of the gap H2 of the filling squeegee 10 isscraped by the scraping squeegee 14 a. Through the scraping by thescraping squeegee 14 a, the unnecessary solder paste 7 on the surface 3a of the mask 3 is removed, so that the solder paste 7 filled in theopenings 4 to swell over the surface 3 a is turned to be even with thesurface 3 a.

[0091] Thereafter, the printed board 5 is separated from the mask 3 toprint the solder paste 7. In the left printing similar to the rightprinting, after the printed board 5 is positioned and overlapped withthe mask 3, the filling squeegee 10 and the left scraping squeegee 14 bare lowered by the up-down driving devices 11 and 16. In this case also,the front end part 20 of the scraping squeegee 14 b are brought in touchwith the surface 3 a of the mask 3 with a suitable pressing force, whilethe filling squeegee 10 is not in direct touch with the surface 3 a ofthe mask 3 with maintaining the gap H2 of the predetermined size h2. Thefilling squeegee 10 is lowered so that the gap H2 is positioned behindthe solder paste 7 in the printing direction leftward. The subsequentoperations are carried out in the same manner as in the right printing.

[0092] The above-described printing operations are repeated alternately,whereby the solder paste 7 is continuously printed and applied on lands6 of the printed board 5 via the mask 3.

[0093] According to the present embodiment, the side face 21 of thescraping squeegee 14 a, 14 b is inclined with an optional acute orobtuse angle to the surface 3 a of the mask 3 at the time of actualprinting thereby to scrape unnecessary solder paste 7. However, thescraping squeegee 14 a, 14 b may be inclined beforehand axially to thesurface 3 a of the mask 3, concretely, so that the side face 21 of thesqueegee 14 a, 14 b may be inclined beforehand with an optional acute orobtuse angle, as will be described hereinbelow.

[0094] More specifically, in a solder paste printing apparatus 501 shownin FIG. 9, the scraping squeegees 14 a, 14 b are held by holders 507,510 which are set to holding members 506, 509 fitted to driving shafts15 a, 16 a of the up-down driving devices 15, 16 via pins 505, 508. Thepins 505, 508 are arranged coaxially with the driving shafts 15 a, 16 a,supporting the holders 507, 510 so that the holders 507, 510 can swingin the left and right printing directions to the holding members 506,509. In consequence, the side face 21 of each scraping squeegee 14 a, 14b can be set to the surface 3 a of the mask 3 with an optional angle ina range from an acute angle to right angles to an obtuse angle. The pins505, 508 are, for instance, constituted of clamping members such asbolts and nuts. The holders 507, 510 are stopped to swing and thesqueegees 14 a, 14 b are fixed at the optional angle by clamping of thepins 505, 508.

[0095] The holders 507, 510 may be adapted to swing centering the pins505, 508 by a known mechanism using, e.g., a motor or the like therebyto be fixed at the optional angle.

[0096] As described hereinabove, the pins 505, 508, holding members 506,509 and holders 507, 510 constitute angle setting devices 502, 503 forthe scraping squeegees 14 a, 14 b.

[0097] The solder paste printing apparatus 501 of FIG. 9 is in the sameconstitution except the above points as the printing apparatus 51described with reference to FIG. 1.

[0098] In the case where the side face 21 of the scraping squeegee 14 a,14 b is set, for example, at an obtuse angle to the surface 3 a of themask 3, as indicated in FIG. 11, the unnecessary solder paste 7 on thesurface 3 a can be removed without influencing to the utmost the solderpaste 7 filled in the openings 4 of the mask 3 by the filling squeegee10. The reason will be made clear with reference to FIG. 12 showing ageneral shearing model of cutting a structure 521 by a tool 520. Whenthe structure 521 is cut by the tool 520 as shown as the above model, ashear force by the tool 520 acts mainly to an upper part than a finishface 522, namely, a shaded shear area 524 in FIG. 12. That is, the shearforce acts only to a portion which becomes a chip part 523. Therefore,in FIG. 12, if the tool 520 is replaced with the scraping squeegee 14 a,14 b, the work 521 lower than the finish face 522 with the solder paste7 filled in the openings 4, and the chip part 523 with the unnecessarysolder paste 7 on the surface 3 a, the shear force acts solely to theunnecessary solder paste 7 on the surface 3 a when the side face 21 ofthe scraping squeegee is set at an obtuse angle, and accordingly theunnecessary solder paste 7 on the surface 3 a can be removed withoutaffecting the solder paste 7 filled in the openings 4.

[0099] On the other hand, when the side face 21 of the scraping squeegee14 a, 14 b is set to be an acute angle to the surface 3 a of the mask 3,the following effect is obtained. For instance, even when the solderpaste 7 is filled insufficiently by the filling squeegee 10 to theopenings 4 thereby forming the non-filled parts 9, the solder paste 7can be surely filled in the openings 4 by the scraping squeegee 14 a, 14b with the acute angle. That is, when the scraping squeegee 14 a, 14 bis set with the acute angle as in FIG. 13, not only the filling squeegee10, but the scraping squeegee 14 a, 14 b supplementarily produces thefilling pressure. Therefore, the scraping squeegee 14 a, 14 b can beeffective to re-fill the solder paste 7 to the openings 4 where thenon-filled parts 9 are present and at the same time, remove theunnecessary solder paste 7 on the surface 3 a.

[0100] As shown in FIGS. 14-16, the same effect as described above canbe attained also when the side face 21 is set with an obtuse angle orright angles to the surface 3 a. That is, when, depending on theconfiguration of the front end part 20 of each of the squeegee 14 a, 14b, an angle of the face 21 a which is arranged beforehand in theprinting direction and is separated from the side face 21 is acute tothe surface 3 a as compared with the front end part 20 of the scrapingsqueegee 14 b being brought in touch with the surface 3 a, even thoughan angle of the side face 21 is set to be obtuse or right angle, theeffect similar to that in a case where the angle is acute can beobtained. The solder paste 7 is filled to the openings 4 mainly by thefilling squeegee 10, while the scraping squeegee 14 a, 14 b assists thefilling. Therefore, it is enough that the filling pressure generated bythe scraping squeegee 14 a, 14 b is smaller than that of the fillingsqueegee 10, thereby allowing the side face 21 of the squeegee 14 a, 14b to be set with a large angle, without inviting the issue as when thesqueegee angle a is reduced in the conventional squeegee. The non-filledpart 9 can be prevented even when the squeegee speed is enhanced, andstable printing can be achieved.

[0101] Further, as indicated in a schematic view of an upper face of themask in FIG. 10, the scraping squeegee 14 a, 14 b is preferably arrangedso that a line of contact 515 between the front end part 20 of thesqueegee and the surface 3 a of the mask 3 is not parallel to anextending direction of a side edge part defining the opening 4 in themask 3. The openings 4 of the mask 3 are sometimes formed in a patternso that the extending direction of the side edge part defining theopening 4 is linear and a straight part 4 a is formed having itsextending direction orthogonal to a printing direction shown by anarrow. In this state, if the scraping squeegee 14 a, 14 b is moved inthe printing direction while an extending direction of the line ofcontact 515 is orthogonal to the printing direction, namely, theextending direction of the line of contact 515 is in parallel to theextending direction of the straight part 4 a, the front end part 20 ofthe scraping squeegee 14 a, 14 b is caught by the straight part 4 a ofthe opening 4 of the mask 3, whereby the front end part 20 or opening 4is possibly broken. Therefore, the scraping squeegee 14 a, 14 b ispreferably fitted to the driving shaft 15 a, 16 b of the up-down drivingdevice 15, 16 so that an angle 516 of the extending direction of theline of contact 515 to the extending direction of the straight part 4 ais acute or an angle 517 is obtuse to let the extending direction of theline of contact 515 intersect with the extending direction of the sideedge part defining the opening 4. The above angle 516 is preferablyapproximately 1 to 45°, most preferably 45°.

[0102] The scraping squeegee 14 a, 14 b may be fitted to the drivingshaft 15 a, 16 b in a manner to make the angle 516, 517 changeable.

[0103] In the foregoing embodiment, the scraping squeegee 14 a, 14 b isorientated to the mask 3 so that the openings 4 of the mask 3 are notparallel to the extending direction of the line of contact 515. Oppositeto the above, the mask 3 may be shifted to the scraping squeegee 14 a,14 b so as to make the straight part 4 a not parallel to the line ofcontact 515 with the extending direction of the line of contact 515 keptorthogonal to the printing direction.

[0104] In the event that the openings 4 of the mask 3 are formed inpattern not to have the straight parts 4 a parallel to the extendingdirection of the line of contact 515, it is unnecessary to orient thescraping squeegee 14 a, 14 b, for example, to assume the acute angle516.

[0105] In the embodiment as above, the reaction force detector 13 is setto the driving shaft 11 a of the up-down driving device 11 for thefilling squeegee 10 to detect the reaction force of the solder paste 7acting to the whole face of the filling squeegee 10. However, thefilling pressure by the solder paste 7 to the opening 4 can be detecteddirectly in a constitution as will be described below.

[0106] In a solder paste printing apparatus 535 shown in FIG. 17, afilling squeegee 530 corresponding to the above filling squeegee 10generally includes, similar to the filling squeegee 10, a filling member531 corresponding to the filling member 22 and a holding member 23holding the filling member 531, and is coupled to the driving shaft 11 aof the up-down driving device 11, for the filling squeegee 530, mountedto the bed plate 17. The up-down driving device 11 is connected to acontrol device 536 and is driven via the control device 536, as will bedetailed later, based on information of outputs of a pressure detector532 a or 532 b such as a pressure detecting sensor thereby to raise orlower the driving shaft 11 a.

[0107] As shown in FIGS. 18 and 19, the pressure detector 532 a, 532 bis built in the filling member 531 in the vicinity of approximately thecenter in an axial direction of the filling member 531 and at a frontend part 534 of the filling member 531 inside a filling pressuring face533. The pressure detector 532 a, 532 b is set at a position where thesolder paste 7 is present at the time of printing so as to detect thefilling pressure generated when the solder paste 7 is filled in theopenings 4 by the filling squeegee 530. At least one detector isprovided for each filling pressuring face 533. As described earlier, thefilling pressure shows a maximum value in the distribution in thevicinity of the front end 534 of the filling member 531, and thereforethe pressure detector 532 a, 532 b is preferably set in the vicinity ofthe front end 534 of the filling member 531. Moreover, in order to morecorrectly detect the filling pressure, the pressure detector 532 a, 532b is built in the filling member 531 so as to have its pressuredetection face exposed to the filling pressuring face 533 as illustratedin the drawings.

[0108] The other structure of the solder paste printing apparatus 535 inFIG. 17 is equal to those of the solder paste printing apparatuses 51,501 shown in FIGS. 1 and 9, except the above points.

[0109] A difference of the reaction force detector 13 of the printingapparatus 51 and the pressure detectors 532 a, 532 b of the printingapparatus 535 in the above embodiments will now be described. Althoughboth detectors are installed to detect a state change of the fillingpressure of the solder paste 7 at the time of printing, the pressuredetector 532 a, 532 b directly detects the filling pressure, whereas thereaction force detector 13 detects the reaction force which is a sum ofthe filling pressures acting to the whole face of the filling pressuringface 25, in other words, detects the filling pressure indirectly.

[0110] Even when the filling pressure is the same, the reaction forcedetector 13 detects the reaction force different in accordance with anarea of the filling pressuring face 25. For example, if a size of thefilling member 22 is changed to fit the printed board 5, it takes a lotof labor to refer to the previously accumulated information of reactionforces, thus causing to reproduce printing conditions. Needless to say,it is easy to refer to the previously accumulated information unless thearea of the filling pressuring face 25 is changed when the same fillingmember 22 is used. On the other hand, since the filling pressure isdetected directly with the use of the pressure detector 532 a, 532 b,the previously detected information of pressures can be readily referredto even if the filling member 531 is changed in size, whereby printingconditions can be reproduced easily, which is preferable.

[0111] The thus-constituted printing apparatus 535 operates in the samemanner to print the solder paste as the printing apparatus 51 of theabove embodiment. Fundamentally, the “reaction force” in steps 3, 4 inFIG. 8 is replaced with the “pressure”. More specifically, the fillingpressure generated when the solder paste 7 is filled in the openings 4by the filling squeegee 530 is detected by the pressure detector 532 ain step 3, and whether or not the detected pressure is, for instance,within a preliminarily set value range is judged in step 4. If thedetected pressure is outside the proper range, in step 5, the controldevice 536 drives at least one of the up-down driving device 11 andangle variable device 12 so as to set the detected pressure in theproper range. In consequence, at least one of the height andintersection angle of the filling squeegee 530 is changed.

[0112] The other operations than the above are the same as in theprinting apparatus 51. The solder paste 7 is continuously printed andapplied onto lands 6 of the printed board 5 via the mask 3 through thealternate repetition of the above operations.

[0113] In the foregoing description, only one of the reaction forcedetector 13 and the pressure detectors 532 a, 532 b is arranged in theapparatus. However, both of the detectors may be set in the printingapparatus to detect both the reaction force and the filling pressure.

[0114] According to the solder paste printing apparatus according to thefirst aspect of the present invention and the solder paste printingmethod according to the second aspect of the present invention, as isfully described above, the filling squeegee and scraping squeegees areprovided. The filling squeegee is moved in a state without contact withthe surface of the mask thereby to fill the solder paste in openings ofthe mask, then the unnecessary solder paste on the mask is removed bythe scraping squeegee. Accordingly, the solder paste is prevented frombeing filled in the openings defectively or scraped improperly even whenthe squeegee speed is increased, so that the solder paste can be printedstably on the circuit board. The print time can be reduced, therebyimproving productivity.

[0115] The entire disclosure of Japanese Patent Applications No.8-329758 filed on Dec. 10, 1996 and No. 9-134778 filed on May 26, 1997,including specification, claims, drawings, and summary are incorporatedherein by reference in its entirety.

[0116] Although the present invention has been fully described inconnection with the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

What is claimed is:
 1. A solder paste printing apparatus wherein asqueegee device moves in a printing direction to a surface of a maskhaving openings formed therein, thereby to print and apply solder pasteon the surface via the openings to a face of a circuit board positionedat a rear face of the mask, said squeegee device comprising: a fillingsqueegee having a front end kept in a noncontact state via a gap to thesurface at the time of printing, and filling the solder paste into theopenings while moving in the printing direction; and a scraping squeegeearranged behind the filling squeegee in the printing direction, movingin the same direction as the filling squeegee while keeping touch withthe surface at the time of printing thereby to remove unnecessary solderpaste on the surface.
 2. A solder paste printing apparatus according toclaim 1 , wherein the scraping squeegee is provided for each directionbehind the filling squeegee with respect to the printing direction in acase where the squeegee reciprocates to the surface of the mask.
 3. Asolder paste printing apparatus according to claim 2 , wherein thefilling squeegee is divided to two in the printing direction.
 4. Asolder paste printing apparatus according to claim 1 , furthercomprising an angle setting device for setting the scraping squeegee sothat an angle of the scraping squeegee in an axial direction thereof tothe surface of the mask is an optional acute or obtuse angle.
 5. Asolder paste printing apparatus according to claim 4 , wherein thescraping squeegee is inclined with the obtuse angle by the angle settingdevice.
 6. A solder paste printing apparatus according to claim 4 ,wherein the scraping squeegee is inclined with the acute angle by theangle setting device thereby to fill the solder paste into the openingsas well as remove the unnecessary solder paste.
 7. A solder pasteprinting apparatus according to claim 1 , wherein the scraping squeegeeis disposed so that an extending direction of a line of contact betweenthe scraping squeegee and the surface of the mask intersects with anextending direction of a side edge part defining one of the openings. 8.A solder paste printing apparatus according to claim 1 , wherein a faceof the filling squeegee opposite to the surface of the mask forms afilling pressuring face which is inclined upward from the front end inthe printing direction so as to press the solder paste to the surfaceand fill the solder paste to the openings.
 9. A solder paste printingapparatus according to claim 8 , further comprising a filling adjustmentdevice for adjusting filling of the solder paste to the openings byvarying at least one of a size of the gap and an intersection angle ofthe filling pressuring face and the surface.
 10. A solder paste printingapparatus according to claim 9 , further comprising a filling pressuredetector for detecting a change of a filling pressure of the solderpaste filled into the openings at the time of printing, and a controldevice for controlling the filling adjustment device based on thefilling pressure detected by the filling pressure detector.
 11. A solderpaste printing apparatus according to claim 10 , wherein the fillingpressure detector is a reaction force detector for detecting a reactionforce which is a sum of the filling pressures of the solder paste actingto the whole filling pressuring face at the time of printing.
 12. Asolder paste printing apparatus according to claim 10 , wherein thefilling pressure detector is a pressure detector set at the fillingpressuring face for detecting the filling pressure of the solder pastedirectly.
 13. A solder paste printing method comprising: moving afilling squeegee in a printing direction at time of printing whilekeeping a front end of the filling squeegee in a noncontact state via agap to a surface of a mask having openings formed therein, therebyfilling a solder paste on the surface to the openings; and removingunnecessary solder paste on the surface by a scraping squeegee moving intouch with the surface in the printing direction.
 14. A solder pasteprinting method according to claim 13 , wherein the scraping squeegee isset so that an angle of the scraping squeegee in an axial directionthereof to the surface of the mask is an optional acute or obtuse angle.15. A solder paste printing method according to claim 14 , wherein, whenthe scraping squeegee is set with the obtuse angle, the scrapingsqueegee removes the unnecessary solder paste without adverselyinfluencing the solder paste filled in the openings.
 16. A solder pasteprinting method according to claim 14 , wherein, when the scrapingsqueegee is set with the acute angle, the scraping squeegee fills thesolder paste to the openings as well as removes the unnecessary solderpaste.
 17. A solder paste printing method according to claim 13 ,wherein the scraping squeegee is set so that an extending direction of aline of contact between the scraping squeegee and the surface of themask intersects with an extending direction of a side edge part definingone of the openings.
 18. A solder paste printing method according toclaim 13 , wherein a face of the filling squeegee opposite to thesurface of the mask forms a filling pressuring face which is inclinedupward from the front end in the printing direction so as to press thesolder paste to the surface and fill the solder paste to the openings.19. A solder paste printing method according to claim 18 , wherein achange of a filling pressure of the solder paste when the solder pasteis filled by the filling squeegee to the openings at the time ofprinting is detected by a filling pressure detector, and at least one ofan intersection angle of the filling pressuring face and the surface anda size of the gap is adjusted based on the detected filling pressure,thereby to change printing condition.